Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/02—Power saving arrangements
  • H04W52/0209—Power saving arrangements in terminal devices
  • H04W52/0212—Power saving arrangements in terminal devices managed by the network, e.g. network or access point is master and terminal is slave
  • H04W52/0216—Power saving arrangements in terminal devices managed by the network, e.g. network or access point is master and terminal is slave using a pre-established activity schedule, e.g. traffic indication frame
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
  • H04W4/70—Services for machine-to-machine communication [M2M] or machine type communication [MTC]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/02—Power saving arrangements
  • H04W52/0209—Power saving arrangements in terminal devices
  • H04W52/0225—Power saving arrangements in terminal devices using monitoring of external events, e.g. the presence of a signal
  • H04W52/0229—Power saving arrangements in terminal devices using monitoring of external events, e.g. the presence of a signal where the received signal is a wanted signal
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W68/00—User notification, e.g. alerting and paging, for incoming communication, change of service or the like
  • H04W68/02—Arrangements for increasing efficiency of notification or paging channel
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W76/00—Connection management
  • H04W76/20—Manipulation of established connections
  • H04W76/28—Discontinuous transmission [DTX]; Discontinuous reception [DRX]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
  • H04W88/02—Terminal devices
  • H04W88/06—Terminal devices adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
  • Y02D30/00—Reducing energy consumption in communication networks
  • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

• the present invention relates to a method, terminal device, base station, wireless telecommunications system and method therefor
• Third and fourth generation mobile telecommunication systems such as those based on the 3 GPP defined UMTS and Long Term Evolution (LTE) architectures, are able to support more sophisticated services than simple voice and messaging services offered by previous generations of mobile telecommunication systems.
• LTE Long Term Evolution
• third and fourth generation networks are therefore strong and the coverage areas for these networks is expected to increase rapidly.
• MTC machine type communication
• smart meters which, for example, might be located in a customer's house and periodically transmit information back to a central MTC server relating to the customer's consumption of a utility, such as gas, water, electricity and so on. Further information on characteristics of MTC-type devices can be found, for example, in the 30 corresponding standards, such as ETSI TS 122 368 V10.530 (201 1-07) / 3 GPP TS 22.368 version 10.5.0 Release 10) [1].
• MTC type terminal devices / MTC type data might include, for example, characteristics such as low mobility, high delay tolerance, small data transmissions, a level of predictability for traffic usage and timing (i.e. traffic profile), relatively infrequent transmissions and group-based features, policing and addressing.
• an MTC-type terminal is preferably relatively simple and inexpensive and able to operate with relatively low power consumption. For example, it may often be the case that an MTC-type terminal is required to operate for an extended period of time without an external source of power.
• an MTC-type terminal whilst it can be convenient for an MTC-type terminal to take advantage of the wide coverage area and robust communications interface provided by third or fourth generation mobile telecommunication networks, there are aspects of these networks which are not well suited to simple and inexpensive devices. This is because such networks are generally optimised for use by devices that require high data rates and low latency. Although power usage is an important consideration for such devices, it is to some extent of secondary concern to issues of data rates and latency.
• the type of functions performed by a typical MTC-type terminal on the other hand (for instance collecting and reporting back data on a relatively infrequent basis) do not typically require high data rates furthermore are typically not time- critical.
• the inventors have recognised a desire to allow certain types of terminal device to operate within a mobile telecommunications network with lower power consumption than other conventional terminal devices operating within the network.
• a method of operating a terminal device in a wireless telecommunications system which, during a mode transition state, supports a first mode of operation where the terminal device does not communicate with the wireless telecommunications system and a second mode of operation where the terminal device does communicate with the wireless
• telecommunications system the method comprising:
• a method of operating a base station in a wireless telecommunications system which, during a mode transition state, supports a first mode of operation where the base station does not communicate with the terminal device and a second mode of operation where the base station does communicate with the terminal device, the method comprising: transitioning from the first mode of operation to the second mode of operation at the expiration of a time period whereby the time period is defined by the data traffic pattern to the terminal device.
• a terminal device for use in a wireless telecommunications system which, during a mode transition state, supports a first mode of operation where the terminal device does not communicate with the wireless telecommunications system and a second mode of operation where the terminal device does communicate with the wireless telecommunications system
• the terminal device comprising: a transceiver unit configured to communicate with the wireless telecommunications system and a processor unit configured to control the transceiver unit to transition from the first mode of operation to the second mode of operation at the expiration of a time period whereby the time period is defined by the data traffic pattern to the terminal device.
• a base station for use in a wireless telecommunications system which, during a mode transition state, supports a first mode of operation where the base station does not communicate with a terminal device and a second mode of operation where the base station does communicate with the terminal device, the base station comprising: a transceiver unit configured to communicate with the terminal device and a processor unit configured to control the transceiver unit to transition from the first mode of operation to the second mode of operation at the expiration of a time period whereby the time period is defined by the data traffic pattern to the terminal device.
• Figure 1 schematically represents an example of a conventional LTE-type wireless telecommunication network
• Figure 2 schematically represents some aspects of a conventional LTE radio frame structure
• Figure 3 schematically represents some aspects of a conventional LTE downlink radio 15 subframe
• Figures 4 to 6 schematically represent some aspects of a conventional discontinuous reception (DRX) mode of a wireless telecommunication network
• Figure 7 shows a timing diagram explaining the RRC state transition from the RRC Idle mode to the RRC Connected mode
• Figure 8 shows a timing diagram explaining the release procdure from the RRC connected mode to the RRC idle mode
• Figure 9 shows a flow chart explaining embodiments of the disclosure
• Figures 10A and 10B show diagrams displaying the arrival of packets in a typical Poisson process
• Figure 12A shows a flow chart explaining the process for the SPRST stage from the RAN side
• Figure 12B shows a flow chart explaining the process for the SPRST stage from the terminal device side;
• Figure 13A and 13B shows two alternative mechanisms for the base station 101 and terminal device 104 to enter the SPRST stage;
• Figure 14 shows a timing diagram of the RRC release procedure
• Figure 15 shows a timing diagram of the RRC connection establishment procedure
• Figures 16A and 16B show the last RRC connection establishment procedure for the expiration of the SPRST stage
• Figure 17 shows a flowchart explaining the issuance of a release message from the base station to the terminal device.
• Figure 18 schematically represents some aspects of a wireless telecommunication network configured to operate in accordance with certain embodiments of the present disclosure
• Figure 1 provides a schematic diagram illustrating some basic functionality of a wireless
• the network includes a plurality of base stations 101 connected to a core network 102.
• Each base station provides a coverage area 103 (i.e. a cell) within which data can be communicated to and from terminal devices 104.
• Data are transmitted from base stations 101 to terminal devices 104 within their respective coverage areas 103 via a radio downlink.
• Data are transmitted from terminal devices 104 to the base stations 101 via a radio uplink.
• the core network 102 routes data to and from the terminal devices 104 via the respective base stations 101 and provides functions such as authentication, mobility management, charging and so on.
• Terminal devices may also be referred to as mobile stations, user equipment (UE), user terminal, mobile radio, in this context MTC UE and so forth.
• Base stations may also be referred to as transceiver stations / nodeBs / e-NodeBs/ eNBs, and so forth.
• FIG. 2 shows a schematic diagram illustrating an OFDM based LTE downlink radio frame 201.
• the LTE downlink radio frame is transmitted from an LTE base station (known as an enhanced Node B) and lasts 10 ms.
• the downlink radio frame comprises ten subframes, each subframe 20 lasting 1 ms.
• FIG. 3 is a schematic diagram of a grid which illustrates the structure of an example conventional downlink LTE subframe (corresponding in this example to the first, i.e. left-most, subframe in the frame of Figure 2).
• the subframe comprises a predetermined number of symbols which are transmitted over a lms period. Each symbol comprises a predetermined number of orthogonal sub-carriers distributed across the bandwidth of the downlink radio carrier.
• the example subframe shown in Figure 3 comprises 14 symbols and 1200 sub-carriers spread 30 across a 20MHz bandwidth.
• the smallest allocation of user data for transmission in LTE is a resource block comprising twelve sub-carriers transmitted over one slot (0.5 subframe).
• each individual resource element (a resource element comprises a single symbol on a single subcarrier) is not shown, instead each individual box in the subframe grid corresponds to twelve sub-carriers transmitted on one symbol.
• Figure 3 shows resource allocations for four LTE terminals 340, 341, 342, 343.
• the resource allocation 342 for a first LTE terminal extends over five blocks of twelve sub-carriers (i.e. 60 sub- carriers)
• the resource allocation 343 for a second LTE terminal extends over six blocks of twelve sub-carriers and so on.
• Control channel data are transmitted in a control region 300 (indicated by dotted- shading in Figure 3) of the subframe comprising the first n symbols of the subframe where n can vary between one and three symbols for channel bandwidths of 3MHz or greater and where n can vary between two and four symbols for channel bandwidths of 1.4MHz.
• the data transmitted in the control region 300 includes data transmitted on the physical downlink control channel (PDCCH), the physical control format indicator channel (PCFICH) and the physical HARQ indicator channel (PHICH).
• PDCCH physical downlink control channel
• PCFICH physical control format indicator channel
• PHICH physical HARQ indicator channel
• PDCCH contains control data indicating which sub-carriers on which symbols of the subframe have been allocated to specific LTE terminals.
• the PDCCH data transmitted in the control region 300 of the subframe shown in Figure 3 would indicate that UE1 has been allocated the block of resources identified by reference numeral 342, that UE2 has been allocated the block of resources identified by reference numeral 343, and so on.
• PCFICH contains control data indicating the size of the control region (i.e. between one and three symbols).
• PHICH contains HARQ (Hybrid Automatic Request) data indicating whether or not previously transmitted uplink data has been successfully received by the network.
• HARQ Hybrid Automatic Request
• Symbols in a central band 310 of the time- frequency resource grid are used for the transmission of information including the primary synchronisation signal (PSS), the secondary synchronisation signal (SSS) and the physical broadcast channel (PBCH).
• This central band 310 is typically 72 sub-carriers wide (corresponding to a transmission bandwidth of 1.08 MHz).
• the PSS and SSS are synchronisation signals that once detected allow an LTE terminal device to achieve frame synchronisation and determine the cell identity of the enhanced Node B transmitting the downlink signal.
• the PBCH carries information about the cell, comprising a master information block (MIB) that includes parameters that LTE terminals use to properly access the cell. Data transmitted to individual LTE terminals on the physical downlink shared channel (PDSCH) can be transmitted in other resource elements of the subframe.
• MIB master information block
• Figure 3 also shows a region of PDSCH containing system information and extending over a bandwidth of R344.
• a conventional LTE frame will also include reference signals which are not shown in Figure 3 in the interests of clarity.
• the number of sub-carriers in an LTE channel can vary depending on the configuration of the transmission network. Typically this variation is from 72 sub carriers contained within a 1.4MHz channel bandwidth to 1200 sub-carriers contained within a 20MHz channel bandwidth (as schematically shown in Figure 3).
• Data transmitted on the PDCCH, PCFICH and PHICH is typically distributed on the sub- carriers across the entire bandwidth of the subframe to provide for frequency diversity.
• a terminal device in radio resource control (RRC) connected mode and RRC Idle mode receives and decodes PDCCH in subframes to identify if there are any transmission resource allocations (resource grants) for the terminal device in the subframe.
• RRC radio resource control
• a terminal device is thus required to receive and decode PDCCH for all subframes in which the terminal device might potentially be allocated transmission resources, even though in many of these subframes there might not be any data for the terminal device.
• Resources used in receiving and decoding PDCCH in subframes for which there is no data for the terminal device are in effect wasted.
• DRX techniques involve a terminal device and a base station in effect agreeing times (e.g. particular subframes) during which the terminal device will be monitoring downlink physical channels and the base station can expect the terminal device to receive transmissions sent to it.
• the terminal device thus knows that outside these agreed times there are subframes when it will not receive transmissions from the base station, and the terminal device may conserve power during these subframes by not receiving and decoding PDCCH.
• a DRX mode comprises alternating periods during which a terminal device could potentially receive data from the base station (and hence should monitor PDCCH) and periods during which the terminal device will not receive data (and hence need not monitor PDCCH to save power).
• the subframes in which the terminal device could receive data from the base station may be referred to as DRX inactive periods and the subframes in which the terminal device should not receive data from the base station may be referred to a DRX active periods.
• DRX inactive periods and DRX active periods are defined by various parameters (which may be defined in terms of numbers of subframes).
• DRX parameters There are six basic DRX parameters that define the pattern of DRX inactive and DRX active periods in LTE. These are:
• Figures 4 to 6 are schematic diagrams showing how the above-identified DRX parameters are defined on a representative time axis t. (The timings in these figures are represented for clarity of explanation and are not necessarily shown to scale.)
• Figure 4 schematically represents the basic underlying DRX cycle with periods when the terminal device receiver circuitry is active and monitoring PDCCH (DRX inactive) schematically represented by diagonally shaded blocks on the time axis t.
• This aspect of the LTE DRX mode may be referred to herein as the "normal" or "basic" DRX cycle / mode.
• the timings relating to this normal DRX cycle are set by the parameters DRX Cycle and On Duration Timer as schematically represented in the figure.
• a terminal device activates its receiver circuitry and monitors PDCCH for a period corresponding to On Duration Timer once every DRX Cycle.
• a relatively long basic DRX cycle allows for more power to be conserved.
• a long basic DRX cycle also results in increased latency because there are longer periods of time during which the terminal device is not monitoring PDCCH (and hence cannot be contacted).
• To address this LTE provides for two durations of DRX cycle, namely the basic / normal DRX cycle represented in Figure 4, and a shorter
• the short DRX cycle is broadly similar to the normal DRX cycle in overall structure in that it also comprises a regular pattern of DRX inactive and DRX active periods. However, the short DRX cycle adopts a shorter repeat period.
• the operation of the short DRX cycle is governed by the parameters DRX Short Cycle and DRX Short Cycle Timer.
• DRX Short Cycle is the repeat period for the short DRX cycle (DRX Cycle is an integer multiple of DRX Short Cycle in LTE).
• DRX Short Cycle timer defines the number of short DRX cycle periods before the normal DRX cycle is entered. (In LTE the On Duration Timer applies for both short and normal DRX cycles.)
• a terminal device which has concluded communicating with a network initially enters the short DRX cycle mode before entering the longer / normal DRX cycle mode (assuming no communications are made during the period established by DRX Short cycle Timer).
• the principle underlying this approach in LTE is a recognition that a terminal device is more likely to need to re-communicate with a network relatively soon after a previous communication, and so a shorter DRX cycle can be used to reduce latency for a period after a recent communication. If, however, the terminal device does not re-communicate with the base station during this period, the terminal device may then drop into the longer normal DRX cycle.
• Figure 5 schematically represents some aspects of the short DRX cycle in LTE.
• Figure 5 is similar to, and will be understood from, Figure 4, except the left-most DRX cycle in Figure 4 is replaced in Figure 5 with a section of short DRX cycle mode.
• the DRX Short Cycle is one-half the normal DRX Cycle.
• the DRX Short Cycle Timer in this particular timing example is taken to expire at the end of the second DRX Short Cycle represented in Figure 5 such that the normal (longer) DRX cycle, as represented in Figure 4, picks up from this point.
• the DRX mode comprises a number of short cycles followed by a longer DRX opportunity until the next DRX cycle begins.
• LTE defines various non-repeating / irregular DRX inactive periods during which a terminal device is required to monitor PDCCH, and these are schematically represented in Figure 6.
• the upper part of Figure 6 is a timeline representing various periods during which a terminal device receiver is active while the lower part of Figure 6 is a corresponding timeline representing periods during which the terminal device transmitter is active.
• Figure 6 uses blocks to identify times at which the terminal device is required to monitor PDCCH.
• the terminal device receives a downlink communication on PDSCH.
• This may be any conventional downlink communication.
• the receipt of a downlink communication initiates a timer during which a terminal device is required to continue monitoring PDCCH, even if the On Duration Timer associated with the normal regular and repeating DRX cycle expires.
• This timer is set by the DRX Inactivity Timer parameter.
• the DRX Inactivity Timer causes the DRX inactive period during which the terminal device must monitor PDCCH to be extended beyond the "normal" DRX inactive period if a downlink communication is received during the "normal" inactive period. This is schematically represented by the grid shading in Figure 6 for the leftmost DRX inactive period.
• the DRX Inactivity Timer is reset, thereby extending the DRX inactive period further still. Only once the DRX Inactivity Timer expires can the terminal device reenter DRX active mode.
• the network may also send a DRX command to allow the terminal device to enter the DRX opportunity.
• the network may set the logic channel ID (LCID) in the MAC sub-header as "1 1 1 10" [3], [4]. Once the UE receives the command, the UE will go to sleep.
• LCID logic channel ID
• the terminal device In response to the PDSCH allocation represented in the left-most DRX inactive period in the upper part of Figure 6, the terminal device will, in accordance with conventional techniques, transmit uplink acknowledgement signalling (ACK/NACK signalling) for the (schematically represented in the lower part of Figure 6 by the chequer-board shaded block).
• ACK/NACK signalling uplink acknowledgement signalling
• the terminal device sends its acknowledgement signalling four sub frames after the subframe containing the relevant PDSCH allocation. If the terminal device is unable to properly decode the PDSCH allocation it will transmit negative acknowledgement (NACK) signalling.
• NACK negative acknowledgement
• the base station schedules a retransmission of the information comprising the PDCCH allocation.
• the base station has some flexibility with regards to rescheduling the retransmission.
• the base station cannot reschedule the transmission before a time set by HARQ RTT Timer (e.g. eight subframes) after the initial PDSCH allocation has expired, but the base station does not need to schedule the retransmission in the subframe immediately after HARQ RTT Timer expires.
• HARQ RTT Timer e.g. eight subframes
• the terminal device must reactivate its receiver circuitry when HARQ RTT Timer expires in the expectation that the base station will at some stage after HARQ RTT Timer expires schedule a retransmission of the information sent in the previous PDSCH allocation.
• the parameter DRX Retransmission Timer specifies the amount of time the terminal device must remain active after expiry of HARQ RTT Timer to monitor PDCCH for a resource allocation for a retransmission of the earlier PDSCH allocation that was negatively acknowledged. This period of time during which the terminal device cannot remain in DRX active mode is schematically represented in Figure 6 by the block with dotted shading.
• a retransmission of a previous negatively-acknowledged PDSCH allocation may be expected to occur during the period corresponding to the DRX Retransmission Timer, and this will require the terminal device to remain in an active mode monitoring PDCCH waiting for the retransmission to be received on PDSCH or for the DRX Retransmission Timer to expire.
• Figure 6 represents how the repeating and regular pattern of active and inactive DRX periods of Figures 4 and 5 becomes disrupted when a terminal device receives downlink communications and how this result in additional periods of time during which the terminal device must monitor PDCCH.
• the right-hand half of Figure 6 represents another situation which results in a terminal device needing to monitor PDCCH outside the repeating and regular pattern of active and inactive DRX periods such as represented in Figures 4 and 5. This is triggered by the terminal device making a scheduling request (SR) with an uplink transmission on the physical uplink control channel (PUCCH). A terminal device will typically do this when it wishes to request uplink resources because the terminal device has data it needs to communicate to the network.
• the PDCCH SR is schematically represented in the lower part of Figure 6 by the brick-shaded block.
• a terminal device When a terminal device transmits a SR on PUCCH it can expect to receive a response from the base station on PDSCH. In order to receive the response, the terminal device must therefore monitor PDCCH for the PDSCH allocation message. That is to say, on sending the PUCCH SR, the terminal device must exit DRX active mode. This is schematically represented in Figure 6 by the by the block with zigzag shading. Once the terminal device receives the PDSCH allocation in response to the PUCCH SR, the DRX Inactivity Timer is restarted as discussed above, and as schematically represented in the right-hand part of the upper timeline in Figure 6.
• Figure 6 represents how the repeating and regular pattern of active and inactive DRX periods of Figures 4 and 5 also becomes disrupted when a terminal device requests uplink resources and how this again results in additional periods of time during which the terminal device must monitor PDCCH.
• the parameters DRX Cycle, On Duration Timer, DRX Short Cycle, DRX Short Cycle Timer, DRX Inactivity Timer, and DRX Retransmission Timer which define the DRX timings are shared between the base station and terminal device through RRC signalling in accordance with conventional techniques.
• the starting point of the DRX cycle i.e. what might be termed its phase relative to the system frame numbering
• DRX Start Offset which is communicated through RRC signalling.
• both the terminal device and the network can determine from the system frame number the particular subframes when the terminal device receiver should be active and listening to PDCCH. This allows the base station to schedule transmissions to the terminal device at the appropriate times and the terminal device to activate its receiver circuitry to receive any such transmissions at the appropriate times. Further information on conventional DRX operation in LTE-type networks can be found in the relevant standards. See, for example, ETSI TS 136 331 VI 1.3.0 (2013-04) / 3 GPP TS 36.331 version 1 1.3.0 Release 11 [5], and ETSI TS 136 321 VI 1.2.0 (2013-04) / 3 GPP TS 36.321 version 1 1.2.0 Release 1 [6].
• the current RRC protocol and DRX operation are designed to target terminal devices with high traffic demands, small latency and high levels of mobility.
• the current RRC protocol and DRX operation does not therefore consider the unique properties of MTC type terminal devices. Typically, these devices have low traffic volume, infrequent and intermittent data bursts and a lack of mobility.
• Figure 6 describes the DRX operation of a terminal device when operating in an RRC Connected mode.
• the terminal device may operate in an RRC Idle mode. In this mode, the terminal device has already registered with the network but is not connected and there is no radio link established between it and the network.
• the terminal device monitors a paging channel to detect incoming calls, acquires system information and performs neighbouring cell measurement and cell reselection.
• the upper layers may configure the terminal device with a terminal device specific DRX.
• the DRX cycle can be from 32 to 256 radio frames and the on duration is 1-4 subframes.
• the terminal device controls its own mobility and its location is only known at Tracking Area level.
• FIG. 7 shows a timing diagram explaining the RRC state transition from the RRC Idle mode to the RRC Connected mode.
• the RRC state transition is explained below.
• the terminal device wakes up to monitor PDCCH in order to search for the presence of a paging message. Once the terminal device finds the Paging Radio Network Temporary Identifier (P-RNTI) then it proceeds to decode the paging message located in PDSCH which is indicated by PDCCH. 2. After decoding the paging message, if the terminal device does not find its own terminal device identity then it returns to DRX operation in the RRC Idle mode. This is shown in the first two paging occasions in Figure 7.
• P-RNTI Paging Radio Network Temporary Identifier
• the terminal device finds its identity in the message it triggers the Random Access Procedure (RAP) followed by the establishment of the RRC Connection, i.e. moving from the RRC Idle mode to the RRC Connected mode.
• RAP Random Access Procedure
• RAP the UE sends a random access preamble to the base station and the base station confirms by sending a random access response (RAR).
• RAP/RRC connection establishment after the UE receives the RAR, a Layer 2/Layer 3 message is scheduled for uplink transmission to the base station on the PUSCH [7]. It conveys the RRC connection request.
• RRC connection establishment the base station sends the RRC connection setup message to the terminal device.
• the DRX operation parameters can be carried in this message.
• RRC connection establishment the terminal device sends back a message indicating the completion of RRC connection setup.
• RRC connection establishment upon reception of this message, the base station can also transmit to the terminal device the RRC messages including security mode command and RRC connection reconfiguration.
• RRC connection establishment the RRC state transition is complete once the terminal device sends back reconfiguration completion message. After this message exchange the RRC connection is established and the terminal device and network enter the RRC connected mode.
• a terminal device inactivity timer is started immediately. It is a vendor-specific implementation choice and indicates the duration after the base station has cleared its Transmission buffer and does not detect any uplink data from the terminal device. In most LTE radio access networks (RAN), it is configured to approximately 10 s.
• RAN radio access networks
• the UE may transmit and receive continuously or it may enter DRX mode. All the DRX operation parameters have been informed by the network via RRC setup or RRC reconfiguration message and listed in Table 1 below.
• drx- Inactivity timer timer is on UE remains in 'ON state' which may extend UE ON period into the period
• the terminal device inactivity timer When the network detects that the terminal device is not transmitting or receiving, the terminal device inactivity timer is activated. After the terminal device inactivity timer expires, an RRC connection release message is sent from the network and the terminal device transitions to the RRC idle mode to save radio resources and battery. This release procedure is shown in Figure 8.
• a terminal device release request is sent to the Mobile Management Entity (MME) 102A.
• the MME 102A sends a Release Access Bearers request to the Serving Gate Way (S-GW) 102B.
• S-GW 102B sends a Release Access Bearers response back to the MME 102A.
• a terminal device Context release command is sent from the MME to the base station 101.
• An RRC connection release is established between the base station 101 and the terminal device 104.
• the base station 101 sends a terminal device context release complete signal to the MME 102A.
• MTC type terminal devices There are several issues with the current transition procedure between RRC Idle and RRC Connected modes and between the RRC Connected and the RRC Idle modes.
• data traffic in MTC type terminal devices is far more infrequent compared with other traffic such as smartphone traffic.
• traffic for MTC type terminal devices may occur from once or twice a minute to once or twice a day. This means that many of the paging occasions are unnecessary and drain the battery of the terminal device.
• the MTC traffic is typically very short in length compared with other traffic. Therefore, in combination with the long period of time between consecutive occurrences of traffic for an MTC type terminal device, the transition between the RRC Connection mode and the RRC Idle mode is almost always repeated (with the corresponding signalling requirements) for a short MTC device packet.
• MTC type terminal devices such as smartmeters and the like have little or no mobility. This is not considered in the current RRC state transition procedure.
• a flow chart 900 describing, in general, embodiments of the present disclosure is shown in Figure 9.
• the flow chart 900 starts at step 905.
• a first stage is conducted in step 910.
• a measurement stage is conducted at step 910.
• the measurement stage will be described with reference to Figures 10A, 10B and 1 1.
• a second stage is conducted in step 915.
• a semi- persistent RRC state transition (SPRST) stage is carried out in step 915.
• the SPRST stage will be described with reference to Figures 12A, 12B, 13A, 13B, 14, 15, 16A, 16B and 17.
• the flow chart then finishes at step 920.
• the inter-arrival times are determined from key traffic parameters.
• the base station 101 measures the key traffic parameters based on network memory.
• the key traffic parameters in this case are traffic parameters that indicate a downlink transmission to the UE. Examples of this may include a paging message having the particular UE identity such as the IMSI (International Mobile Subscriber Identity).
• IMSI International Mobile Subscriber Identity
• the duration of T ms is determined by the base station 101. Assuming a Poisson process for the MTC type terminal device [8], the traffic parameter to be measured is, in embodiments, the mean inter-arrival time Tint. It should be noted that other measures of inter-arrival time are envisaged such as the median inter- arrival time, or any kind of inter-arrival time. As different terminal devices receive downlink
• T ⁇ should be terminal device-specific in the sense that a common number of measuring occasions is defined as N ms and based on different T int . Thus, T ⁇ will be different for different terminal devices.
• the terminal device 104 follows normal procedures in DRX and RRC mode changes. In other words, the terminal device 104 continues reading PDCCH in each DRX cycle and only leaves the RRC Connected mode once it is released by RRC signalling.
• the core network (CN) 102 could collect and measure the traffic parameters for each UE. This could take place, for example, by the core network providing statistics on inter-arrival times for all the radio bearers of a UE.
• T int the next step is to choose appropriate time at which the terminal device and network performs the transition from RRC idle to RRC connected mode. This is defined as Ttrans and is subject to one or more (in any order) of three defined service requirements: delay tolerance, false transmission probability and signalling overhead ratio.
• T d The delay, denoted as T d , is a random variable and the longer the Ttrans, the larger the delay is envisaged.
• T max maximal delay
• T ave average delay
• T P probability delay
• x is the inter-arrival time between packet (i- l) and i except ⁇ . Since all the packets arrived during time (/- l)Ttrans, /Ttrans) are buffered at the eNB 101 and sent until time /Ttrans, the delay of the n-th packet is given as d relieve— lT trans — ⁇ l— l)T trarls — ⁇ x t — T trans — ⁇ x t , (2)
• the inter-arrival time between itself and the previous packet is z ⁇ .
• xi also follows the exponential distribution and is independent with x 2 to x N . This means that d n is irrelevant with / so that we can consider a simplified case as shown in Figure 1 OA and we have
• the interpretation here is the same as with S 2 .
• the joint density does not contain any arrival time other than s n , except for the ordering constraint 0 ⁇ Si ⁇ .. . ⁇ s N +i, and thus this joint density is constant over all choices of arrival times satisfying the ordering constraint.
• This equation reveals a very important conclusion that the distribution of the delay is solely determined by Ttrans and irrelevant with respect to the mean inter-arrival time, i.e. the feature of the Poisson process.
• Figure 1 1 shows the cumulative distribution function (CDF) of the delay for 5, 10, and 20s for different mean arrival time (1 , 5 and 10s). The aforementioned conclusion is confirmed by the perfect match between the curves from Monte-Carlo simulation and theoretical derivation. The distribution of the delay is irrelevant with the distribution of the inter-arrival time but only determined by Ttrans- Then we have
• CDF cumulative distribution function
• This upper limit set the first constraint for the value of ⁇ .
• T tmns T min ⁇ T m ⁇ i , 2T ave ,T P / P ⁇ .(9)
• Pfai is defined as the probability that no data packet arrives during T b!ms so that although the RRC transition is conducted, no data is transmitted after RRC connection is established. Thus, the energy consumed as well as the signalling exchanged is wasted. It has been established by the inventors that the shorter the value of ⁇ , the larger the possibility of no data packet arriving is. ⁇ 3 ⁇ 4 ⁇ can be obtained based on the distribution of the Poisson process as
• ⁇ is a parameter used to represent the expected number of events in a time interval.
• signalling overhead ratio i.e. signalling overhead per packet.
• the MTC traffic is normally intermittent bursty data packets
• the relative amount of signalling over user plane data is usually very large because the RRC connection establishment and release requires a few hundred bytes at a time for very small amount of data to be transmitted.
• ⁇ ' is the mean average of the minimum and maximum value in the range of derived from equation (15). In this case, Trans' is 180.
• N depicts how many maximal DRX cycles would fit into which for a maximal DRX of 2.56 seconds, means N is 70. Therefore, using option 1 , the value of 70 can be depicted with fewer bits than the value of 180.
• . Ttrans ⁇ * ⁇ . In this case, N' is an intermediate value and in this option, the value of N' is also 70.
• N argmin
• option 1 and option 2 have advantages.
• the advantage of the first option is the accuracy of and the advantage of the second option is that less bits are used to indicate N compared with the first option.
• Step 1 - For the intended terminal device, the base station 101 stores the IMSI of the terminal device and sets the measuring time T ⁇ and measuring time counter, n ⁇ to 0.
• Step 2 On the n ms -th measuring occasion, once the base station 101 observes a paging message sent to the terminal device, the base station 101 saves the inter-arrival time T n ms in association with the IMSI of the terminal device.
• Step 4 Using equation 14 and the assumed constraints, the range of ⁇ is determined.
• the base station 101 must know whether a particular terminal device 104 that is being paged is under its cell. This is to ensure that the base station 101 can connect the paging message frequency (to a particular IMSI) with RRC signalling to the terminal device 104 in the cell. This allows the network to move to the SPRST stage. Due to the low mobility (or static) nature of MTC type terminal devices, it is unlikely that the terminal device will be associated with a different base station during the whole Ttrans measurement stage.
• the previous base station 101 can send the value of ⁇ (if calculated) or the values of ⁇ and measuring time T i ns with the handover message to the different base station.
• the terminal device may be released from operating in the SPRST stage and wait until the network re-instructs the terminal device to operate in the SPRST stage again.
• the core network could pass the value of ⁇ to the new base station.
• SPRST Stage After the measurement stage has taken place and the value of T tnms has been calculated, the terminal device 104 enters the SPRST stage where the terminal device 104 enters a state with timers guiding its transfer between the RRC Idle mode and the RRC Connected mode.
• the SPRST stage can be described as follows: The duration of the SPRST stage is determined by a timer T mode at the base station 101. Once the measurement stage is complete, the base station 101 will instruct the terminal device 104 to enter the SPRST mode by sending a positive flag and the RRC transition timer T bims to the terminal device and the timer T mode starts. Once T mode expires, the base station 101 sends a negative flag to notify the terminal device 104 to go back to normal RRC operation. In the SPRST mode, the RRC transition timer ⁇ is held at both the base station 101 and the terminal device.
• the terminal device 104 starts the random access procedure (RAP) by sending the random access (RA) preamble to the base station 101 followed by a RRC establishment procedure and ⁇ is reset immediately.
• RAP random access procedure
• RA random access
• the network automatically performs RRC transition from the RRC idle mode to the RRC connected mode, i.e. the RRC transition happens periodically depending on T b!ms but not on the paging occasions.
• the energy consumed by periodically checking paging message in the RRC idle mode is saved.
• Figure 12A shows a flow chart explaining the process for the SPRST stage from the RAN side and Figure 12B shows a flow chart explaining the process for the SPRST stage from the terminal device side.
• the flow chart 1200 starts at step 1202.
• step 1204 a time indicating the length of time of the SPRST is determined. This time is deemed T mode .
• T mode is the duration of time that the Semi Persistent RRC State Transition (SPRST) is in force. It is a parameter decided by the network when it decides how long to allow a terminal device to stay in a mode where it cannot be reached by the base station apart from every ⁇ when the terminal device wakes up.
• the base station sets a timer with starting value of T mode , and when that timer expires the base station commands the terminal device to return to normal RRC Connected mode with only DRX cycle to provide it power savings.
• the RAN (via the base station 101) sends a positive flag to the terminal device 104 instructing the terminal device 104 to enter the SPRST mode.
• This flag may be sent over the PDSCH.
• the flag may be sent in any appropriate packet or may be sent as a separate packet, but in embodiments, the flag may be sent in either the Random Access Response (msg2) from the base station or in the RRC Connection Setup Message. In the RRC Connection Setup Message, there is room for non- critical extensions which allow adding of further bit fields into the fields of that message.
• the base station 101 starts timer T SPRST at 0 when the base station 101 enters the SPRST mode (the SPRST mode expiring when the value in timer T SPRST equals T mode ).
• the timer T SPRST may start at T mode and count down to 0.
• the value of T mode is the duration of the SPRST mode. This is a parameter value that is fed into the timer
• the RAN (via the base station 101) sends the calculated value to the terminal device. This value is sent during the RRC: Connection setup message, which is carried on PDSCH, signalling between the base station 101 and the terminal device 104. During the period the terminal device 104 does not check the paging message. Any packets which are destined for the terminal device 104 during the period are stored at the base station 101.
• the RAN and the terminal device 104 establish RRC Connected mode at the expiration of the time Ttrans- As the RAN and terminal device 104 establish the RRC Connected mode, the packets stored at the base station 101 are transmitted to the terminal device 104 after the RRC Connected mode has been established.
• a new value may be included in the packets stored at the base station 101.
• the terminal device 104 When the packets are then sent to the terminal device 104 during the RRC Connected mode set at the expiration of the Ttrans period, the terminal device 104 will receive the updated and will use the new value of subsequently. This is step 1212 in Figure 12A.
• the value may be updated in response to a change in the value of determined during the measurement stage.
• the measurement stage does not end when a value of Ttrans is determined.
• the measurement stage continues whenever the terminal device 104 is operating in the SPRST mode. Therefore, the value of Ttrans may be periodically updated.
• the terminal device and RAN may only operate on a new value of when the measured value of Ttrans varies from the operational value of Ttrans by a predetermined amount such as 2% or by some other threshold set either by the Standard or by an MNO. Additionally, or alternatively, the value of Ttrans may be changed in dependence on the stored packets. In this case, if when the terminal device 104 and the base station 101 operate using the RRC Connected mode at the expiration of T bans there are no stored packets, then the value of may be too short. This is especially the case if there are no stored packets for consecutive expired periods of ⁇ .
• the terminal device 104 downloads the stored packets which are destined for the terminal device 104. Therefore, if there are no stored packets, this means no packets are destined for the terminal device 104 during this period and so the period is too short.
• the RAN (via the base station 101) informs the terminal device 104 of the end of the SPRST mode. This is achieved by the RAN sending a negative flag (via the base station 101) to the terminal device 104 to notify the terminal device 104 to return to normal RRC operation. This is step 1214 but will be explained in more detail later. The process ends at step 1216.
• the flow chart 1250 starts at step 1252.
• the terminal device 104 After the terminal device 104 receives the positive flag from the base station 101 (sent in step 1206 of Figure 12A), the terminal device 104 starts operating in the SPSRT mode. This is step 1254.
• the timer T SPRST starts at 0 in the base station 101.
• the T SPRST timer at the terminal devices starts as soon as it receives and decodes the message carrying from the base station.
• the UE timer starts at ⁇ , where ⁇ is determined by the propagation and processing delays as explained above. This delay is negligible for the purposes of synchronous operation over SPRST mode between the base station and the terminal device.
• step 1256 the terminal device 104 remains silent in the RRC Idle mode and is not activated to check paging messages periodically when the value of ⁇ has not expired.
• step 1258 timer T b!ms expires and the terminal device 104 starts the random access procedure by sending the random access preamble to the base station 101 followed by an RRC establishment procedure. This transitions the terminal device 104 from the RRC Idle mode to the RRC Connected mode. The value of ⁇ TM8 in the timer is reset and the stored data packets are then communicated over the air between the base station 101 and the terminal device 104.
• the terminal device 104 After expiration of time T mode; the terminal device 104 receives the negative flag from the base station 101 (step 1214 of Figure 12A) and the terminal device 104 leaves the SPSRT mode in step 1260. The process ends in step 1262.
• step 1206 of Figure 12A and step 1254 of Figure 12B it is noted that the base station 101 and the terminal device 104 must enter the SPRST mode.
• Two alternative mechanisms for the base station 101 and terminal device 104 to enter the SPRST mode is described with reference to Figure 13A and 13B.
• FIG. 13A Alternative 1 is shown in Figure 13A where a terminal device 104 communicates with a base station 101.
• step 1302 normal DRX is conducted at terminal device side and the terminal device 104 is activated to check paging message every T DRX id i e seconds, where T DRX id i e is the DRX cycle in RRC idle mode.
• the base station 101 receives a paging message from MME (via the base station 104) and sends the paging message to the terminal device 104 and with the paging message, a positive flag (1 bit) indicating the start of SPRST mode is sent as well. This is step 1305 and starts T mode .
• the terminal device 104 sends RA preamble and in step 1307B, the base station 101 sends back RAR.
• step 1309A the terminal device 104 sends RRC connection request and in step 1309B, the base station 101 sends back the RRC connection setup message. Within the message, the DRX timers and the chosen value of ⁇ are included. . In step 1313 the terminal device 104 sends back RRC connection complete message to the base station 101.
• step 1315 the base station 101 sends security mode and RRC reconfiguration message and the terminal device 104 responds.
• the terminal device 104 and the base station 101 are now operating in RRC Connected mode.
• Alternative 2 is shown in Figure 13B where a terminal device 104 communicates with a base station 101.
• step 1352 normal DRX is conducted at the base station side and the terminal device 104 is activated to check paging message every T DRX idle seconds, where T DRX idle is the DRX cycle in RRC idle mode.
• the base station 101 receives a paging message from MME (via the base station 104) and sends the paging message to the terminal device 104.
• the terminal device 104 sends RA preamble and in step 1357B, the base station 101 sends back RAR.
• step 1359A the terminal device 104 sends RRC connection request and in step 1359B, the base station 101 sends back the RRC connection setup message.
• a positive flag (1 bit) indicating the start of SPRST mode is sent as well as the DRX timers and the chosen value of are included. This starts T mode .
• step 1363 the terminal device 104 sends back RRC connection complete message to the base station 101.
• step 1365 the base station 101 sends security mode and RRC reconfiguration message and the terminal device 104 responds.
• the terminal device 104 and the base station 101 are now operating in RRC Connected mode.
• the terminal device 104 starts to transmit and receive data.
• a terminal device inactivity timer is required to instruct the terminal device 104 to return to the RRC Idle mode.
• the terminal device inactivity timer is not required.
• the base station 101 sends a RRC release message and the terminal device 104 enters the DRX mode and waits for the RRC release message. Without the terminal device activity timer, the terminal device 104 is expected to stay in DRX mode of the RRC Connected mode for a very short time before returning to the RRC Idle mode.
• the proposed RRC release procedure is shown in Figure 14.
• step 1402 the base station 101 sends the RRC release message to the terminal device 104.
• the terminal device 104 then transits to the RRC Idle mode as instructed by the base station 101.
• the terminal device 104 will not be activated periodically to check the paging information because the data transmission for a given terminal device 104 only happens at a given time when T bans expires.
• a flow chart 1500 describing the RRC connection establishment procedure is shown.
• the terminal device 104 As the terminal device 104 is operating in the SPRST mode, the terminal device 104 remains silent and does not check the paging message 1502. Therefore, if the base station 101 receives packets from the MME before expires, the packet goes to the buffer in the base station 101 for storage therein. Of course, the packets may be stored at the CN or RAN level if the CN or RAN control the SPRST mode. The terminal device 104 remains silent. Once Ttrans expires at the terminal device 104, the terminal device 104 sends the RA preamble and the base station 101 sends back the RAR. This is step 1504.
• the terminal device 104 sends the RRC connection request and the base station 101 sends back the RRC connection setup message. This is step 1506. Within the message, can be included. The terminal device 104 sends back the RRC connection complete message to the base station 101 in step 1508.
• the base station 101 sends security mode and RRC reconfiguration message to the terminal device 104 in step 1510. Ttrans may also be transmitted here.
• step 1512 the terminal device 104 sends responses to the base station 101.
• the same process as described with reference to Figure 14 is followed.
• the base station 101 knows the SPRST mode should be switched back to normal RRC procedure. In order to achieve this, the base station 101 notifies the terminal device 104 to do so by sending a negative flag. Similar to the first RRC connection
• the negative flag may be carried by RAR response or may be carried in the RRC connection setup request message.
• the last RRC connection establishment procedure is shown in Figure 16A and Figure 16B. Specifically, the first option is shown in Figure 16A and the second option is shown in Figure 16B.
• a flow chart 1600 describing the first option for the last RRC connection establishment procedure is shown.
• the terminal device 104 As the terminal device 104 is operating in the SPRST mode, the terminal device 104 remains silent and does not check the paging message 1602. Therefore, if the base station 101 receives packets from the MME before expires, the packet goes to the buffer in the base station 101 for storage therein. The MTC UE remains silent.
• the terminal device 104 sends the RA preamble and the base station 101 sends back the RAR.
• the RAR in this case a 1 bit negative flag is included that indicates that this is the last RRC connection establishment procedure. This is step 1604.
• the terminal device 104 sends the RRC connection request and the base station 101 sends back the RRC connection setup message. This is step 1606. Within the message, Ttrans can be included.
• the terminal device 104 sends back the RRC connection complete message to the base station 101 in step 1608.
• the base station 101 sends security mode and RRC reconfiguration message to the terminal device 104 in step 1610. ⁇ may also be transmitted here.
• the terminal device 104 sends responses to the base station 101.
• FIG. 16B a flow chart 1650 describing the second option for the last RRC connection establishment procedure is shown.
• the terminal device 104 As the terminal device 104 is operating in the SPRST mode, the terminal device 104 remains silent and does not check the paging message 1652. Therefore, if the base station 101 receives packets from the MME 102 before expires, the packet goes to the buffer in the base station 101 for storage therein. The terminal device 104 remains silent.
• the terminal device 104 sends the RA preamble and the base station 101 sends back the RAR. This is step 1654.
• the terminal device 104 sends the RRC connection request and the base station 101 sends back the RRC connection setup message. This is step 1656.
• Ttrans can be included.
• a 1 bit negative flag is included that indicates that this is the last RRC connection establishment procedure.
• the terminal device 104 sends back the RRC connection complete message to the base station 101 in step 1658.
• the base station 101 sends security mode and RRC reconfiguration message to the terminal device 104 in step 1660.
• Tt j -ans may also be transmitted here.
• step 1662 the terminal device 104 sends responses to the base station 101.
• the terminal device 104 After execution of the steps shown in either Figure 16A or 16B, the terminal device 104 will operate in the RRC Connected mode. In order to transition from the RRC Connected mode to the RRC Idle mode, a release message is sent from the base station 101 to the terminal device 104. This is shown in Figure 17.
• Figure 17 shows a flowchart 1700 explaining the issuance of a release message from the base station 101 to the terminal device 104.
• the base station 101 sends a release message to the terminal device 104 in step 1702.
• the terminal device 104 transitions to the RRC Idle mode in step 1704.
• the terminal device 104 then enters the DRX state and checks the paging message every T DRX _ Id i e seconds in step 1706.
• monitoring the paging occasions in the RRC idle mode is not required because for each terminal device 104, the RRC transition time is fixed and known to itself.
• the terminal device 104 can just wake up at given time to receive the data directed to it.
• the base station 101 acts as the main node controlling the SPRST scheme and determining the parameters, it can perform the measurement or estimation (based on CN information) of traffic simultaneously and adaptively adjust the parameters based on the measurement results (or information provided by CN) to achieve a subtle balance between latency and energy consumption.
• the CN or RAN act as the controlling node for the SPRST scheme as is envisaged.
• DRX is basically a MAC layer operation targeting to the terminal devices with high traffic demand and normal mobility.
• Other optimization schemes such as baseband procedure optimization and power amplifier optimization, focus on physical layer and hardware.
• the proposed scheme happens in the RRC layer.
• FIG 18 schematically shows a telecommunications system 500 according to an embodiment of the present disclosure.
• the telecommunications system 500 in this example is based broadly around an LTE- type architecture. As such many aspects of the operation of the telecommunications system 500 are known and understood and are not described here in detail in the interest of brevity. Operational aspects of the telecommunications system 500 which are not specifically described herein may be implemented in accordance with any known techniques, for example according to the current LTE-standards.
• the telecommunications system 500 comprises a core network part (evolved packet core) 502 coupled to a radio network part.
• the radio network part comprises a base station (evolved- nodeB) 504 coupled to a plurality of terminal devices.
• a base station evolved- nodeB
• two terminal devices are shown, namely a first terminal device 506 and a second terminal device 508.
• the radio network part may comprise a plurality of base stations 30 serving a larger number of terminal devices across various communication cells. However, only a single base station and two terminal devices are shown in Figure 18 in the interests of simplicity.
• the terminal devices 506, 508 are arranged to communicate data to and from the base station (transceiver station) 504.
• the base station is in 35 turn communicatively connected to a serving gateway, S-GW, (not shown) in the core network part which is arranged to perform routing and management of mobile communications services to the terminal devices in the telecommunications system 500 via the base station 504.
• S-GW serving gateway
• the core network part 502 also includes a mobility management entity (not shown) which manages the enhanced packet service, EPS, connections with the terminal devices 506, 508 operating in the communications system based on subscriber information stored in a home subscriber server, HSS.
• EPS enhanced packet service
• PCRF policy charging and resource function
• PDN-GW packet data network gateway
• the first terminal device 506 is a conventional smartphone type terminal device communicating with the base station 504 in a conventional manner.
• This conventional terminal device 506 comprises a transceiver unit 506a for transmission and reception of wireless signals and a processor unit 506b configured to control the device 506.
• the processor unit 506b may comprise a processor unit which is suitably configured / programmed to provide the desired functionality using conventional programming / configuration techniques for equipment in wireless telecommunications systems.
• the transceiver unit 506a 20 and the processor unit 506b are schematically shown in Figure 7 as separate elements.
• the functionality of these units can be provided in various different ways, for example using a single suitably programmed general purpose computer, or suitably configured application-specific integrated circuit(s) / circuitry.
• the conventional terminal device 506 will in general comprise various other elements associated with its operating functionality.
• the second terminal device 508 is a machine-type communication (MTC) terminal device 504 adapted to support operation in accordance with embodiments of the present disclosure when communicating with the base station 504.
• machine -type communication terminal devices can in some cases be typically characterised as semi-autonomous or autonomous wireless communication devices communicating small amounts of data. Examples include so-called smart meters which, for example, may be located in a customer's house and periodically transmit information back to a central MTC server data relating to the customer's consumption of a utility such as gas, water, electricity and so on.
• MTC devices may in some respects be seen as devices which can be supported by relatively low bandwidth communication channels having relatively low quality of service (QoS), for example in terms of latency. It is assumed here the MTC terminal device 508 in Figure 18 is such a device.
• QoS quality of service
• the MTC device 508 comprises a transceiver unit 508a for transmission and reception of wireless signals and a processor unit 508b configured to control the MTC device 508.
• the processor unit 508b may comprise various sub-units, for example a DRX control unit, for providing functionality in accordance with embodiments of the present disclosure as explained further herein. These sub-units may be implemented as discrete hardware elements or as appropriately configured functions of the processor unit.
• the processor unit 508b may comprise a processor unit which is suitably configured / programmed to provide the desired functionality described herein using conventional programming / configuration techniques for equipment in wireless telecommunications systems.
• the transceiver unit 508a and the processor unit 508b are schematically shown in Figure 18 as separate elements for ease of representation.
• the MTC device 508 will in general comprise various other elements associated with its operating functionality.
• the base station 504 comprises a transceiver unit 504a for transmission and reception of wireless signals and a processor unit 504b configured to control the base station 504 to operate in accordance with embodiments of the present disclosure as described herein.
• the processor unit 506b may again comprise various sub-units, such as a scheduling unit, for providing functionality in accordance with embodiments of the present disclosure as explained further below.
• the processor unit 504b may comprise a processor unit which is suitably configured / programmed to provide the desired functionality described herein using conventional programming / configuration techniques for equipment in wireless telecommunications systems.
• the transceiver unit 504a and the processor unit 504b are schematically shown in Figure 18 as separate elements for ease of representation.
• the functionality of these units can be provided in various different ways, for example using a single suitably programmed general purpose computer, or suitably configured application-specific integrated circuit(s) / circuitry.
• the base station 504 will in general comprise various other elements associated with its operating functionality.
• the base station 504 is configured to communicate data with both the conventional terminal device 506 and the terminal device 508 according to an embodiment of the disclosure over respective communication links 510, 512.
• the base station 504 is configured to communicate with the conventional terminal device 506 over the associated radio communication link 510 following the established principles of LTE-based communications, and in particular using conventional DRX and RRC procedures.
• communications between the base station 504 and the MTC terminal device 508 operate using modified DRX and RRC procedures in accordance with certain embodiments of the present disclosure as described herein.
• the base station is configured to operate by communicating with different classes of terminal device (e.g. a first class of terminal device, for example comprising conventional LTE terminal devices, such as
• a base station may operate to communicate with a first class (group / type) of terminal device in accordance with a first DRX mode associated first DRX mode timings and to communicate with a second class (group /type) of terminal device in accordance with a second DRX and RRC mode associated second DRX and RRC mode timings, the rules governing the DRX mode timings of the second DRX and RRC modes being different from those of the first DRX and RRC modes.
• Whether or not a particular terminal device or base station supports modified DRX procedures in accordance with embodiments of the present disclosure may be established in accordance with conventional techniques for sharing terminal device and base station capability information in wireless telecommunications network, for example based on signalling exchange during a RRC connection establishment procedure.
• Described embodiments may be implemented in any suitable form including hardware, software, firmware or any combination of these. Described embodiments may optionally be implemented at least partly as computer software running on one or more data processors and/or digital signal processors.
• the elements and components of any embodiment may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the disclosed embodiments may be implemented in a single unit or may be physically and functionally distributed between different units, circuitry and/or processors.
• a method of operating a terminal device in a wireless telecommunications system which, during a mode transition state, supports a first mode of operation where the terminal device does not communicate with the wireless telecommunications system and a second mode of operation where the terminal device does communicate with the wireless telecommunications system, the method comprising:
• a method comprising storing in the wireless telecommunications system, during the first mode of operation, data packets destined for the terminal device; and receiving from the wireless telecommunication system those stored data packets during the second mode of operation.
• T ave is the average delay in communicating the data packet
• T P is an upper bound with probability P for the delay in communicating the data packet.
• Ttrans is the time period
• T int is the inter-arrival time
• Pf a i is the probability that no data packet arrives during the first mode of operation.
• T ttans is the time period
• ⁇ represents the expected number of events in a time interval in a Poisson process.
• a method comprising receiving a representation of a selected value for the time period, the representation being the closest integer number of maximal DRX durations in the selected value of the time period.
• a method comprising receiving a representation of a selected value for the time period, the representation being selected from a sequence of numbers that are powers of two, wherein the selection is closest to the integer number of maximal DRX durations in the selected value of the time period.
• the time period is calculated within one of the base station, a network core or a radio access unit.
• the method further comprises entering the mode transition state and operating in the second mode of the mode transition state.
• a method comprising the steps of: receiving a paging message from the wireless telecommunication network; sending a random access, RA, message to the wireless telecommunication network; receiving an RA response message from the wireless telecommunication network; sending a radio allocation control, RRC, connection request message and receiving an RRC setup message from the wireless telecommunication network, wherein the RRC setup message includes the system flag and the time period value.
• a method according to any one of paragraphs 1 1, 12 or 13 comprising the steps of receiving, from the wireless telecommunication network, an RRC release message and in response to the RRC release message, the method comprises transitioning to the first mode of operation.
• a method according to any one of paragraphs 1 1 to 14, wherein when the terminal device is operating in the second mode of the mode transition state, the method further comprises receiving, from the wireless telecommunications network, a second flag indicating that in response to the next RRC release message, the terminal device will leave the mode transition state.
• a method comprising sending a random access message and receiving from the wireless telecommunication system a random access response message that includes the second flag.
• a method comprising sending a random access message; receiving from the wireless telecommunication system a random access response message; sending a radio allocation control, RRC, connection request message and receiving from the wireless telecommunications system an RRC connection setup message that includes the second flag.
• a method of operating a base station in a wireless telecommunications system which, during a mode transition state, supports a first mode of operation where the base station does not communicate with the terminal device and a second mode of operation where the base station does communicate with the terminal device, the method comprising:
• a method according to paragraph 18, comprising storing in the wireless telecommunications system, during the first mode of operation, data packets destined for the terminal device; and transmitting to the terminal device those stored data packets during the second mode of operation.
• T a is the average delay in communicating the data packet
• T P is an upper bound with probability P for the delay in communicating the data packet.
• Ttrans is the time period
• T int is the inter-arrival time
• P is the probability that no data packet arrives during the first mode of operation.
• ⁇ represents the expected number of events in a time interval in a Poisson process.
• the method further comprises entering the mode transition state and operating in the second mode of the mode transition state.
• a method according to paragraph 28, comprising the steps of: transmitting a paging message to the terminal device; receiving a random access, RA, message from the terminal device; transmitting an RA response message to the terminal device; receiving a radio allocation control, RRC, connection request message and transmitting an RRC setup message to the terminal device, wherein the RRC setup message includes the system flag and the time period value.
• a method according to any one of paragraphs 28, 29 or 30 comprising the steps of transmitting, to the terminal device, an RRC release message and in response to the transmission of the RRC release message, the method comprises transitioning to the first mode of operation.
• the method further comprises transmitting, to the terminal device, a second flag indicating that in response to the next RRC release message, the base station will leave the mode transition state.
• a method according to paragraph 32 comprising receiving a random access message and transmitting to the terminal device a random access response message that includes the second flag.
• a method according to paragraph 33 comprising receiving a random access message; transmitting to the terminal device a random access response message; receiving a radio allocation control, RRC, connection request message and transmitting to the terminal device an RRC connection setup message that includes the second flag.
• a terminal device for use in a wireless telecommunications system which, during a mode transition state, supports a first mode of operation where the terminal device does not communicate with the wireless telecommunications system and a second mode of operation where the terminal device does communicate with the wireless telecommunications system, the terminal device comprising:
• transceiver unit configured to communicate with the wireless telecommunications system and a processor unit configured to control the transceiver unit to transition from the first mode of operation to the second mode of operation at the expiration of a time period whereby the time period is defined by the data traffic pattern to the terminal device.
• a device prior to entering the mode transition state, the time period using which the processor unit is configured to control the transceiver unit is defined in the wireless telecommunications system by:
• the range for the time period is defined in accordance with a delay tolerance in communicating a data packet between the terminal device and the wireless telecommunications system such that the range of the time period complies with the constraint T t rans ⁇ min ⁇ max , 2T av e
• T max is the maximum delay allowed in communicating the data packet
• T ave is the average delay in communicating the data packet
• T P is an upper bound with probability P for the delay in communicating the data packet.
• T t r a n s is the time period
• T int is the inter-arrival time
• P fa i is the probability that no data packet arrives during the first mode of operation.
• T ttans is the time period
• K is the minimum number of packets transmitted during the second mode of operation
• ⁇ represents the expected number of events in a time interval in a Poisson process.
• transceiver unit is configured to receive a representation of a selected value for the time period, the representation being the closest integer number of maximal DRX durations in the selected value of the time period.
• transceiver unit is configured to receive a representation of a selected value for the time period, the representation being selected from a sequence of numbers that are powers of two, wherein the selection is closest to the integer number of maximal DRX durations in the selected value of the time period.
• a device according to any one of paragraphs 34 to 43 wherein the time period is calculated within one of the base station, a network core or a radio access unit.
• the transceiver unit prior to operating in the mode transition state, is configured to:
• the processor unit is configured to enter the mode transition state and to control the transceiver unit to operate in the second mode of the mode transition state.
• the transceiver unit is configured to receive a system flag and the time period value with a paging message from the wireless telecommunication network.
• the transceiver unit is configured to receive a paging message from the wireless telecommunication network; send a random access, RA, message to the wireless telecommunication network; receive an RA response message from the wireless
• RRC setup message includes the system flag and the time period value.
• transceiver unit configured to receive, from the wireless telecommunication network, an RRC release message and in response to the RRC release message, the processor unit is configured to transition to the first mode of operation.
• a device configured to receive, from the wireless telecommunications network, a second flag indicating that in response to the next RRC release message, the processing unit will be configured to leave the mode transition state.
• a device configured to send a random access message and receive from the wireless telecommunication system a random access response message that includes the second flag.
• the transceiver unit is configured to send a random access message; receive from the wireless telecommunication system a random access response message; send a radio allocation control, RRC, connection request message and receive from the wireless telecommunications system an RRC connection setup message that includes the second flag.
• RRC radio allocation control
• a base station for use in a wireless telecommunications system which, during a mode transition state, supports a first mode of operation where the base station does not communicate with a terminal device and a second mode of operation where the base station does communicate with the terminal device, the base station comprising:
• transceiver unit configured to communicate with the terminal device and a processor unit configured to control the transceiver unit to transition from the first mode of operation to the second mode of operation at the expiration of a time period whereby the time period is defined by the data traffic pattern to the terminal device.
• processor unit configured to control the transceiver unit to transition from the first mode of operation to the second mode of operation at the expiration of a time period whereby the time period is defined by the data traffic pattern to the terminal device.
• a base station according to paragraph 53 wherein the data packets are stored in one of the base station in a storage unit, a network core or a radio access unit of the wireless telecommunications system.
• 55. A base station according to any one of paragraphs 52 to 54 wherein, prior to entering the mode transition state, the time period using which the processor unit is configured to control the transceiver unit is defined in the wireless telecommunications system by:
• T ave is the average delay in communicating the data packet
• T P is an upper bound with probability P for the delay in communicating the data packet.
• a base station according to paragraph 55 or 56, wherein the range for the time period is defined in accordance with a probability that no data packet arrives during the first mode of operation such that the range of the time period complies with the constraint
• Ttrans is the time period
• T int is the inter-arrival time
• P is the probability that no data packet arrives during the first mode of operation.
• a base station according to any one of paragraphs 55 to 58, wherein the transceiver unit is configured to transmit a representation of a selected value for the time period, the representation being the closest integer number of maximal DRX durations in the selected value of the time period.
• the transceiver unit is configured to transmit a representation of a selected value for the time period, the representation being selected from a sequence of numbers that are powers of two, wherein the selection is closest to the integer number of maximal DRX durations in the selected value of the time period.
• the time period is calculated within one of the base station, a network core or a radio access unit.
• the processing unit in response to transmitting the flag, is configured to enter the mode transition state and to control the transceiver unit to operate in the second mode of the mode transition state.
• a base station according to paragraph 62, wherein the transceiver unit is configured to transmit a system flag and the time period value with a paging message to the terminal device.
• a base station according to paragraph 63, wherein the transceiver unit is configured to: transmit a paging message to the terminal device; receive a random access, RA, message from the terminal device; transmit an RA response message to the terminal device; receive a radio allocation control, RRC, connection request message and transmit an RRC setup message to the terminal device, wherein the RRC setup message includes the system flag and the time period value.
• RA random access
• RRC radio allocation control
• a base station according to any one of paragraphs 62, 63 or 64 wherein the transceiver unit is configured to transmit, to the terminal device, an RRC release message and in response to the transmission of the RRC release message, the processing unit is configured to transition to the first mode of operation.
• the transceiver unit is configured to transmit, to the terminal device, a second flag indicating that in response to the next RRC release message, processing unit is configured to leave the mode transition state.
• a base station according to paragraph 66 wherein the transceiver unit is configured to receive a random access message and to transmit to the terminal device a random access response message that includes the second flag.
• a base station according to paragraph 67 wherein the transceiver unit is configured to receive a random access message; transmit to the terminal device a random access response message; receive a radio allocation control, RRC, connection request message and transmit to the terminal device an RRC connection setup message that includes the second flag.
• a wireless telecommunication system comprising the terminal device according to any one of paragraphs 35 to 51 and a base station according to any one of paragraphs 52 to 68.

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